MRI studies of neuroanatomical correlates of developmental disorders and normal development are currently underway. To date, MRI findings suggest decreased frontal and temporal lobe volumes in severe conduct disorder patients and increased caudate size in patients with Sydenhams chorea. Ongoing MRI studies show trends for reduced midsagittal area measurements of the corpus callosum in ADHD patients and a reduction in the midsagittal area of the brainstem and pons in schizophrenic patients. O-15 PET and MRI studies of OCD are currently underway to test hypotheses of whether generalized anxiety, disgust and obsessional anxiety are different as evidenced by differences in regional cerebral blood flow and if imaginal exposure and in vivo exposure to obsessions are different in the physiological response elicited. Specific ROIs of interest include the anterior cingulate, orbital frontal cortex, and caudate. O15 PET studies of seven calendar calculating savants and 14 normal controls show higher left parietal blood flow at rest than controls. Analysis of activation date to date indicate that during calendar calculation, savants have less left frontal and more right parietal blood flow change.